The anatomic relationship of the esophageal lead to the left atrium

This study was undertaken to establish the "in vivo" anatomic relationship of the esophageal catheter to the left atrium. Fourteen patients, seven of whom had enlarged left atria, were included in the study. During cardiac catheterization, a bipolar recording catheter was placed in the esophagus; left atrial cineangiograms were then obtained in the posterior-anterior (PA), left anterior oblique (LAO), and lateral views. The distance of the esophageal catheter, in each of four commonly used positions, to the interatrial septum-right atrium was measured in the PA and LAO cineangiograms. The distance from the same catheter positions to the posterior left atrial wall was measured from the lateral view. In all positions and regardless of left atrial size, the catheter clearly lay behind the left atrium and was closer to the left atrial wall than any other cardiac structure, including the interatrial septum. Bipolar electrograms were recorded from the four commonly used esophageal locations; atrial wave amplitude and other parameters of the electrogram deflection did not vary significantly in the different lead positions. We conclude that esophageal electrograms reflect left atrial activity by virtue of the recording electrode's clear proximity to this structure. The amplitude and configuration of the atrial wave itself is generally not useful in determining the position of the esophageal lead.